During the drilling and completion of oil and gas wells, it may be necessary to engage in ancillary operations, such as evaluating the production capabilities of formations intersected by the wellbore. For example, after a well or well interval has been drilled, zones of interest are often tested to determine various formation properties such as permeability, fluid type, fluid quality, fluid density, formation temperature, formation pressure, bubble point, formation pressure gradient, mobility, filtrate viscosity, spherical mobility, coupled compressibility porosity, skin damage (which is an indication of how the mud filtrate has changed the permeability near the wellbore), and anisotropy (which is the ratio of the vertical and horizontal permeabilities). These tests are performed in order to determine whether commercial exploitation of the intersected formations is viable and how to optimize production.
Tools for evaluating formations and fluids in a well bore may take a variety of forms, and the tools may be deployed downhole in a variety of ways. For example, the evaluation tool may include a formation tester having an extendable sampling device, or probe, and pressure sensors. The evaluation tool may include a fluid identification (ID) system with sampling chambers or bottles. The tool may be conveyed downhole on a wireline. Often times an evaluation tool is coupled to a tubular, such as a drill collar, and connected to a drill string used in drilling the borehole. Thus, evaluation and identification of formations and fluids can be achieved during drilling operations with measurement while drilling (MWD) or logging while drilling (LWD) tools. The several components and systems just described are suitable for various combinations as one of skill in the art would understand.
Downhole operation or evaluation systems often require electronics or electronic devices to fully function. Downhole hydrostatic pressures can reach 10,000 psi, and sometimes up to 20,000 psi or above. Therefore, it is well known that the sensitive electronics must be disposed in a pressure housing or vessel to shield the electronics from the downhole pressures, thereby avoiding damage. The pressure vessel also protects the electronics from corrosive and conductive fluids in the downhole environment. Such a pressure vessel may use O-ring seals coupled to a pressure housing, with iconel used to maintain a rigid vessel and good seal surfaces while in a corrosive environment. The pressure vessel creates a significant pressure differential inside the downhole tool. Such pressure vessels increase the complexity and expense of the downhole tool, and use valuable space in the constrained downhole tool.